Results 1 to 15 of 21

Thread: Pickup coil wires p & n

Hybrid View

Previous Post Previous Post   Next Post Next Post
  1. #1
    Fuel Injected! S.O.B.B.'s Avatar
    Join Date
    Nov 2017
    Location
    Ontario Canada
    Posts
    167

    Pickup coil wires p & n

    After much searching and reading I've found a fair bit of info on this.looking at new large cap hei distributors I see which color wire goes to which pin on the 7 pin icm.my understanding of the pickup coil is that the rotation direction affects the output signal for triggering a spark event.it puts out a wave that is converted to square wave and the trigger should come from the later side just before it drops again.and having the p and n wires backwards would mean it gets the trigger signal from the beginning of the square wave rather than the end where it's desired.I hope I understand this correctly. My question is looking at a corvette large cap hei the icm pickup is wired the same as my cadillac 4.5 distributor but they rotate in opposite directions. Which has left me confused. Is it the ecm that configuration that decides which signal or at which part of the square wave is the trigger. I also found a diagram for megasquirt and it shows the pickup coil wired opposite of the factory wiring.so more confusion. So which way should my set up be wired.my distributor rotates ccw and is wired like factory.but my ecm came from a sbc that rotated cw.the symptom I've had since day one has felt like the timing just isn't right and no matter where it's adjusted or how well it runs it just feels like it has this miss to it.in checking plugs I don't have any that stand out looking different from each other.if anyone with knowledge of this can help that would be great.
    Jeeper
    87 sjimmy powered by a 92 cadillac 4.9L pfi on 7427pcm /700r4/ 8.8 3.55 rear/disc brakes.

  2. #2
    Fuel Injected! S.O.B.B.'s Avatar
    Join Date
    Nov 2017
    Location
    Ontario Canada
    Posts
    167
    20171109_210509.jpgew7hei.gif the pic is wired same as factory.second pic is wired opposite
    Last edited by S.O.B.B.; 06-11-2018 at 08:20 PM.
    Jeeper
    87 sjimmy powered by a 92 cadillac 4.9L pfi on 7427pcm /700r4/ 8.8 3.55 rear/disc brakes.

  3. #3
    Fuel Injected! S.O.B.B.'s Avatar
    Join Date
    Nov 2017
    Location
    Ontario Canada
    Posts
    167
    Can someone point me in the right direction.my engine call for 10° initial advance.at what degree of Crank rotation should the reluctor line up with the tabs on the pick up coil.should it be at 10°btdc that they line up?or more like 30°btdc?as in initial set up of a new to me distributor.any help would be greatly appreciated.thanks
    Jeeper
    87 sjimmy powered by a 92 cadillac 4.9L pfi on 7427pcm /700r4/ 8.8 3.55 rear/disc brakes.

  4. #4
    Fuel Injected! S.O.B.B.'s Avatar
    Join Date
    Nov 2017
    Location
    Ontario Canada
    Posts
    167
    Well today I played with my distributor. I tried setting the distributor to 0°TDC and changed it in my bin aswell.felt same.I also swapped back to smaller injectors and did a few logs to get the fuel close again.I also tried a chip with all spark latency set to Zero and entire timing table to 20° of advance.I went through the rpm range in the latency table and marked what I got.it said I was getting 30°and the timing light confirmed it.I was trying to figure out if the latency table I'm using is way off.the laptop agreed with the data.but it's not what was requested in my bin.I was getting lots of knock count at higher rpm and map.seems I also get a count when I shift. Anyway it still has a felling of a slight miss.like something not firing at the right time and this has bend a problem since day one of this conversion.so I looked at a few pics I took b4 of the small cap and large cap distributors.I think I'm onto the problem but just need to rest my brain and bit and figure out how to rectify this.small cap dizzy the rotor does not point at and plug terminal when the pickup coil is aligned.it's kinda in the middle of two plug terminals.on the large cap the rotor is aligned with a plug terminal when the pickup coil is aligned. So I'm figuring this is the cause of my miss feeling. Any input would be good input.
    Jeeper
    87 sjimmy powered by a 92 cadillac 4.9L pfi on 7427pcm /700r4/ 8.8 3.55 rear/disc brakes.

  5. #5
    Fuel Injected! S.O.B.B.'s Avatar
    Join Date
    Nov 2017
    Location
    Ontario Canada
    Posts
    167
    Jeeper
    87 sjimmy powered by a 92 cadillac 4.9L pfi on 7427pcm /700r4/ 8.8 3.55 rear/disc brakes.

  6. #6
    Fuel Injected!
    Join Date
    Jul 2013
    Location
    Newzealand
    Posts
    483
    If you have the positive and negative backwards it will retard timing as rpm rises and will misfire and carry on no matter what you do tuning wise

Similar Threads

  1. Coil per cylinder 4.3?
    By ericjon262 in forum OBDII Tuning
    Replies: 54
    Last Post: 02-20-2019, 05:15 AM
  2. Throttle body passage for injector wires
    By Bart_3500 in forum GM EFI Systems
    Replies: 5
    Last Post: 12-14-2017, 12:49 AM
  3. LS1 coil packs
    By JeepsAndGuns in forum Buy - Sell - Trade - Wanted
    Replies: 1
    Last Post: 01-12-2016, 02:57 AM
  4. 91 tbi no wires in d1 or d2
    By bigcountry in forum GM EFI Systems
    Replies: 3
    Last Post: 01-06-2015, 07:32 PM
  5. Which wires need swapping? 1228746 to 12287747
    By JoeBobJr in forum GM EFI Systems
    Replies: 1
    Last Post: 01-02-2012, 02:09 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •